1. Field of the Invention
The present invention relates to optical devices. More specifically, the present invention relates to laser amplifiers.
2. Description of the Related Art
High-energy lasers are used in a variety of applications. For example, laser weapon applications currently require output power levels ranging from tens of kilowatts to a few megawatts. To date, only chemical lasers have been scaled to the megawatt level. Unfortunately, chemical lasers are very large and produce toxic byproducts making them unsuitable for many applications.
Compact, efficient, diode-pumped solid-state lasers have been considered for such high power applications. However, these lasers are typically limited to a few kilowatts per laser crystal due to both the limited size of available crystal materials and the challenges in removing the waste heat form the gain medium. These limitations have led to approaches to solid-state high-energy lasers (HELs), which require complex arrangements of large numbers of amplifiers in series or series/parallel configurations.
Planar waveguide geometry (PWG) has emerged as a gain medium geometry well-suited suited to extending the output power from a single solid-state laser module to the MW level, but available materials and fabrication processes are a limitation to the ultimate PWG size and output power. Fabrication of planar waveguides capable of high average power is currently a slow process and has only been scaled to relatively short (approximately 250 mm) lengths due to the lack of growth processes for longer YAG (yttrium-aluminum-garnet) material. Bulk single crystal materials that are available in larger sizes do not have suitable properties for scaling to high power laser operation. Ceramic YAG offers long term potential for availability in larger sizes, but scatter and absorption losses in ceramic YAG are still higher than desired and ceramic YAG material is currently limited to about 350 mm in length.
Some applicable fabrication processes have been developed. Onyx Optics developed a proprietary ‘adhesive free’ bonding process for bonding optical materials. Onyx Optics has fabricated some all Yttrium-Aluminum-Garnet (YAG) planar waveguides up to 250 mm long and some sapphire-clad YAG planar waveguides up to 60 mm long. Similar processes have been demonstrated by Precision Photonics up to 100 mm length. Very small planar waveguide amplifiers have been created by diffusion doping of dopants into both crystalline and glass substrates. Unfortunately, none of these approaches appears to offer scalability to weapon-class power levels.
Hence, a need remains in the art for a system or method for a simple, safe, and yet effective system or method for generating high energy laser outputs at low cost.